That desertion, along with recent killings and captures of other top leaders – as well as the revelation of the inside workings of the rebels through seized computer files – show a weakened and fractured force, but analysts say it would be a mistake for the conservative US-backed government of President Álvaro Uribe to claim victory.

Nelly Avila Moreno, better known as "Karina" said that after 24 years as a member of the FARC she decided to turn herself in to authorities because she and her troops were besieged by the Army and she feared any one of her comrades would give her up for the $2 million bounty on her head.

"The decision I made was because of the pressure of the Army in the area," she told reporters at a news conference Monday in Colombia's second largest city, Medellín.

The government, which has made it a cornerstone of its policies to bring the rebels to their knees, has been using a three-pronged strategy of military pressure, incentives to demobilize, and rewards for the death or capture of top commanders of the rebel army, which is funded largely through cocaine trafficking and kidnapping.

A besieged rebel force...

According to the government, more than 475 FARC fighters have been captured this year alone and nearly 500 have been killed in combat, including the FARC's No. 2 leader, Raúl Reyes, in a March 1 bombing raid of a rebel camp in Ecuador.

But more than by those losses, analysts say, the FARC's morale is hurt by desertions and internal fighting.

"This is obviously a very big blow to the morale of the guerrillas because Karina was a symbol of dedication and enthusiasm for the rebel cause," says Alfredo Rangel, director of the Security and Democracy Foundation in Bogotá. "This will lower morale among a lot of people and motivate them to desert as well."

More than 860 FARC fighters have turned themselves in since the start of the year claiming hunger, exhaustion, fear, and futility.

Late last year, one guerrilla fighter commandeered a small plane from the jungle area where she was stationed to flee the rebels.

Karina had been under the command of senior FARC leader Iván Ríos, who was murdered in his sleep last March by a member of his own security guard who then turned himself in and was granted a $1 million reward.

... a PR coup for the president...

Since then, Karina said, she slept uneasily.

"There, a lot of the rebels think about the economic situation and since so much money was offered for my life, that gets you thinking," she said.

Karina said that she had been cut off from most of her unit for months and had had no contact with the commanding secretariat for two years.

"I don't know what the state of the FARC is on a national level, but we are fractured," she told reporters. She then urged other fighters to follow her lead in turning themselves in.

For Mr. Uribe, Karina's desertion and statements are a major new propaganda coup, following the death of Mr. Ríos and Mr. Reyes and the discovery of a treasure trove of information about the inner workings of the FARC and their alleged relations with neighboring Venezuela and Ecuador.

Jorge Restrepo, director of the Center for Resources for Conflict Analysis in Bogotá says the FARC are not so much breaking up as regionalizing.

"In some areas the guerrillas are more isolated than ever, in others they maintain their capacity," he says, adding that the government could take advantage of that to negotiate regional demobilizations and peace deals.

... but FARC still lives

But Luís Eladio Perez, a former hostage who was released along with three other politicians in February after six years as a rebel captive, says the FARC – which is labeled a terrorist organization by the US and Europe – are not as weak or demoralized as the government would like to portray. "They maintain a political proposal. They are an organized military organization," he says.

With an estimated 9,000 fighters – down from a peak of about 17,000 – the FARC still form a formidable force.

And the rebels are still holding more than 40 high-profile hostages, including three American defence contractors and French-Colombian politician Ingrid Betancourt, who they want to swap for jailed rebel commanders.

The government has rejected rebel demands for a haven to negotiate the swap and with all the recent victories the government may toughen its stance.

Carlos Lozano, editor of the Communist Party weekly Voz, says that the government should not discard the possibility of a negotiation. "The government should not feel emboldened by this, nor think that the solution is to crush the guerrillas militarily," he says. "But the guerrillas should also understand that they have to be open to a political solution to the conflict."